State and federal authorities are joining the investigation into a rash of suspicious fires in Somerville.
There have been nine fires in Somerville in the last eight weeks, including a massive seven-alarm blaze in July that displaced 30 people.
Three have been ruled arsons, and another three are considered suspicious.
Somerville Mayor Joe Curtatone says the state fire marshal is offering a $5,000 reward for information.
"The city of Somerville is offering up to an additional $10,000 for anyone with information that leads to the arrest and prosecution of any individual associated with these fires," he said.
Curtatone says authorities with the FBI and ATF are also investigating.
This program aired on August 19, 2013. The audio for this program is not available.