Hurricane Maria made landfall Wednesday morning in southeast Puerto Rico as a strong Category 4 storm, the National Hurricane Center said.
Maria slammed the island with winds of 155 mph, just 2 mph short of Category 5 status, near the city of Yabucoa. The storm was
Calls for rescue immediately started pouring in. But first responders weren't expected to help right away; they'd planned to head indoors when sustained winds reached 50 mph.
Thousands of Puerto Ricans did heed calls to go to emergency shelters. "As of 2:30 a.m. we count 10,059 refugees and 189 pets (in shelters)," the island's governor, Ricardo Rosselló, tweeted.
Maria became the first hurricane of Category 4 strength or higher in nearly 80 years to hit the US territory, home to 3.3 million people.
Conditions were expected to worsen between 8 a.m. and 9 a.m. ET Wednesday, when the storm's eye wall -- and its strongest winds -- were due to hit the island's eastern coast.
As residents hunkered down in homes and shelters ahead of the direct impact, others in the most vulnerable, low-lying, flood-prone areas were evacuated.
The Puerto Rico Convention Center in San Juan -- which was still housing Hurricane Irma evacuees from other Caribbean islands -- prepared to accept thousands more residents.
Potentially 'strongest ever' stormThe storm was likely to be a record-breaking event, CNN meteorologist Derek Van Dam said.
"This could potentially be the strongest hurricane to ever reach the shores of Puerto Rico," he said from San Juan, Puerto Rico's capital.
"A lot of people remember or have heard of the storms that hit in 1928 and 1930. Well, guess what? This could pale those in comparison. ... It will go down in the record books."
Storm surges of 6 to 9 feet were expected.