The death toll in Puerto Rico attributed to Hurricane Maria has reached 43, an official said on Tuesday, up from 39 previously reported, as islanders continue to fall victim to infections, bad road conditions and other consequences of the storm.

Ramon Rosario, secretary of public affairs and public policy, also told reporters that the island now has 16 per cent of electricity service restored, up from 15 per cent on Monday.

Maria slammed into the Caribbean island on Sept. 20 as the most powerful hurricane to hit the U.S. territory in nearly 90 years. It knocked out electricity to the whole island and caused widespread damage to homes and infrastructure.

Less than 33 per cent of the island's cellphone towers have been restored, according to official data, and it is expected to take months to get the power grid back up.

The death toll could continue to rise, as many of Puerto Rico's 3.4 million residents, particularly in rural areas, struggle without basic necessities or access to hospitals.

Of the four newly reported deaths, one was a person who was operated on for an infection but died, another was killed in a car accident caused by road damage and a third died when a damaged roof fell on him while he was clearing debris from a road, Rosario said. He did not give details of the fourth death.