Located 8km (five miles) north of Grenada, the "Kick ’em Jenny" volcano stirred over March 11-12.
An exclusion zone has been enforced by Grenada’s National Disaster Management Agency after raising the threat level to orange.
An orange alert suggests an eruption is possible within 24 hours. Ships and other marine operators are urged to avoid the area.
The UWI Seismic Research Centre in Trinidad said it recorded a substantial increase in earthquake activity associated with the volcano over the weekend.
Jenny last erupted in April 2017.
The Caribbean Disaster Emergency Management Agency (CDEMA) has said there is no immediate tsunami threat to any participating CDEMA states.
All marine vessels should stay outside the first 1.5km (one-mile) exclusion zone, the CDEMA has said. Non-essential shipping, such as pleasure crafts, should stay at least 5km clear (3.1 miles).
Specific advice for Grenada states vessels should strictly observe the 5km exclusion zone.
The Barbados Department of Emergency Management says while the volcano poses no "immediate threat" to Barbados, ships and marine operators should observe the exclusion zone.
Islanders in St Vincent and the Grenadines have been advised of the increased alert level.
Kick ’em Jenny rises 1,300m from the sea floor on the Lesser Antilles Ridge and is one of the most active volcanoes in the Caribbean.