SAUGUS – A three-alarm fire at 66 Water St. Thursday morning sent two firefighters to Melrose-Wakefield Hospital with minor injuries, according to Deputy Fire Chief Michael Newbury.Newbury declined to identify the firefighters, whom he said were treated for “burns and blood pressure.” After leaving the scene, Newbury went to the hospital to check on them.He said the blaze started at 10 a.m. in the second floor eaves and spread to the attic before punching through the roof. Police blocked off the section of road between Walnut Street and Farm Street in Wakefield.”The fire was so intense that we had to issue a mayday,” said Newbury, adding that, at one point, firefighters were ordered to evacuate the residence.According to the department’s call log, seven outside departments as well as Massport were dispatched to Water Street.Newbury said no one was at home when the blaze started, but that resident Mary Pike came home while it was in progress and was “distraught.” She was not available for comment.Newbury said Revere firefighters were able to rescue Pike’s Chihuahua after finding the animal hiding under a bed. He said the dog was examined by animal control and is expected to survive.The department reported that the fire was “knocked down” by 11:04 a.m. The cause is under investigation.