SAN JUAN, Puer­to Rico — Hur­ri­cane Irene cut pow­er to more than a mil­lion peo­ple in Puer­to Rico, down­ing trees and flood­ing streets on Mon­day, and fore­cast­ers warned it could be a major storm as it threat­ens Flori­da and South Car­oli­na by the end of the week.

There were no reports of deaths or major injuries in Puer­to Rico, but Gov. Luis For­tuno declared a state of emer­gency and urged peo­ple to stay indoors to avoid downed pow­er lines, flood­ed streets and oth­er hazards.

“This isn’t the time to go out to find out what hap­pened … This is the time to stay in your homes,” For­tuno said at a news conference.

The first hur­ri­cane of the Atlantic storm sea­son posed an imme­di­ate threat to the north­east­ern coast of the Domini­can Repub­lic, though the cen­ter of the hur­ri­cane was expect­ed to miss neigh­bor­ing Haiti, which shares the island of His­pan­io­la. Near­ly 600,000 Haitians are still home­less due to the Jan­u­ary 2010 earth­quake and that coun­try could still see heavy rain and trop­i­cal-storm-force winds, said Den­nis Felt­gen, a spokesman for the U.S. Nation­al Hur­ri­cane Cen­ter in Miami.

“We don’t expect for this to get ripped up over the moun­tains of His­pan­io­la,” Felt­gen said. “We expect it to remain a hurricane.”

The U.S. Nation­al Hur­ri­cane Cen­ter pro­ject­ed that Irene could grow into a Cat­e­go­ry 3 hur­ri­cane with winds of 115 mph (184 kph) over the Bahamas on Thurs­day. And it may car­ry that force north­west along Flori­da’s Atlantic coast and toward a pos­si­ble strike on South Car­oli­na, though the fore­cast­ers warned that by the week­end, the stor­m’s path could vary sig­nif­i­cant­ly from the cur­rent projection.

The hur­ri­cane is expect­ed to pass near or over the Turks and Caicos Islands and the south­east­ern Bahamas on Tuesday.

Author­i­ties in Palm Beach Coun­ty direct­ed staffers to stop rou­tine oper­a­tions Mon­day and switch to storm prepa­ra­tions, includ­ing checks on gen­er­a­tors and com­mu­ni­ca­tions equipment.

“Hur­ri­cane prepa­ra­tions are pret­ty much the order of the day,” said Mike Geier, radi­o­log­i­cal emer­gency pre­pared­ness plan­ner. “We go through a pret­ty exten­sive check­list. It’s prob­a­bly three pages long.”

Offi­cials in Charleston, South Car­oli­na, warned res­i­dents to mon­i­tor Irene close­ly. It has been six years since a hur­ri­cane hit the South Car­oli­na coast, said Joe Farmer of the state Emer­gency Man­age­ment Division.

Hur­ri­cane Irene cen­tered about 50 miles (80 kilo­me­ters) north-north­east of Pun­ta Cana, Domini­can Repub­lic late Mon­day morn­ing and it was mov­ing toward the west-north­west at 12 mph (19 kph). It had max­i­mum sus­tained winds of about 80 mph (130 kph) with high­er gusts, the Hur­ri­cane Cen­ter reported.

In Puer­to Rico, 600 crews spread out across the island to repair top­pled light poles, and the major­i­ty of cus­tomers were expect­ed to have pow­er by late Mon­day, spokesman Car­los Mon­roig said. Schools, most gov­ern­ment offices and many busi­ness­es remained closed. Flights resumed at the inter­na­tion­al air­port in San Juan by midmorning.

Dozens of peo­ple in San Juan sought emer­gency shel­ter ahead of Irene and author­i­ties evac­u­at­ed 150 tourists from the out­ly­ing islands of Cule­bra and Vieques as the storm approached.

The storm entered through the south­east coastal town of Humacao, but emer­gency man­age­ment region­al direc­tor Orlan­do Diaz said the dam­age seemed to be less than he feared.

“We thought things were going to be a bit more trag­ic,” he said. “I was sur­prised that we did­n’t see the amount of rain I expected.”

Irene had pre­vi­ous­ly churned through St. Croix in the U.S. Vir­gin Islands, where more than half of the inhab­i­tants are still with­out pow­er, said Chris­tine Lett, emer­gency man­age­ment spokeswoman.

In the Domini­can Repub­lic, offi­cials assured res­i­dents they had food avail­able for 1.5 mil­lion peo­ple if need­ed. Also, sol­diers and emer­gency man­age­ment crews evac­u­at­ed dozens of res­i­dents from high-risk areas along the south­ern coast.

“We have tak­en all pre­cau­tions,” pres­i­den­tial spokesman Rafael Nunez said.

Many stores in the cap­i­tal of San­to Domin­go closed Sun­day even as peo­ple bought last-minute items like flashlights.

The inter­na­tion­al air­port and oth­ers remained open late Mon­day morn­ing, although dozens of flights had been canceled.

Irene is expect­ed to lash the north­east­ern region of the Domini­can Repub­lic for up to 15 hours, local mete­o­rol­o­gist Miguel Cam­pu­sano said.

In the pop­u­lar tourist city of Pun­ta Cana, emer­gency crews pre­pared for the storm but have not tak­en any spe­cial mea­sures, said Can­dy Gomez, spokes­woman for the Pun­ta Cana resort.

The Hur­ri­cane Cen­ter said the main imped­i­ment to the stor­m’s progress over the next cou­ple of days will be inter­ac­tion with land. If Irene pass­es over His­pan­io­la’s moun­tains or over parts of east­ern Cuba, the storm could weak­en more than cur­rent­ly expected.

“How­ev­er, if the sys­tem ends up mov­ing to the north of both of those land mass­es it could strength­en more than expect­ed,” wrote fore­cast­er Richard Pasch.