In a news briefing on Monday, Mr Mitchell warned: “We are not yet out of the woods.” Grenada has also experienced several power outages, impacting communications and access to government updates.
Maximum sustained winds for the hurricane are near 150mph (241 km/h), according to the NHC’s latest update, as the storm moves west.
A hurricane watch is in effect for Jamaica, which means the region is likely to experience hurricane conditions by Wednesday.
“It is not a joke,” said the prime minister of St Vincent and the Grenadines, Ralph Gonsalves, reminding people of the devastation caused by past hurricanes in the Caribbean.
In a national address from his official residence, Mr Gonsalves said he was seeking shelter in his basement.
“The roof, certainly the old part of the roof, may not survive winds at 150mph. I am making preparations to go downstairs,” he said.
Beryl’s strength has been fluctuating.
The hurricane was upgraded to a category four on Monday after slightly weakening earlier.
The NHC said fluctuations in strength were likely to continue but warned that portions of the Windward islands should prepare for “potentially catastrophic wind damage”.
It said St Vincent and the Grenadines as well as Grenada were at the highest risk of damage.
Hurricane shelters opened at 18:00 local time (22:00 GMT) on Sunday.
