Royal Newfoundland Constabulary investigators say two of four house fires in the St. John's area over the weekend may have been deliberately set.

On Saturday, three firefighters were treated in hospital after smoke and heat got the best of them at a blaze on Goodridge Street.

Police said the fire in the Rabbitown area, and one on Beaumont Street about 10 minutes away, could be arson.

Don Byrne, deputy-chief of the St. John's Regional Fire Department, said evidence suggests the fire at Beaumont Street was set by a passerby.

However, he said the fire on Goodridge Street had different origins.

"They're suspicious, quite suspicious, of that one. That particular house was, although we deemed it to be vacant, apparently it was being used by an individual or individuals," said Byrne.

Byrne said it's believed they are both isolated incidents.

The other two fires happened on Third Street in Mount Pearl Saturday afternoon, and on Empire Avenue early Sunday. The Red Cross is helping a number of people affected by those fires.

Pleasure boat destroyed

Meanwhile, a pleasure boat was destroyed by fire in Conception Bay South Monday morning in the waters off Perrin's Road in Manuels.

Police said a call came in shortly after 1:30 a.m. When they arrived they found the Bayliner boat, moored about 15 metres from land, engulfed in flames.

Todd Brophy, the fire chief in C.B.S., said an area resident who happened to be a regional firefighter in St. John's used his boat to tow the pleasure boat ashore.

The C.B.S. fire department managed to put the fire out.

Investigators said it's too early to say what caused the fire.