Firefighters work to extinguish hot spots after a nine-alarm fire at 37-39 Morton St. in Dorchester's Lower Mills section. Image courtesy of the Boston Fire Department.

A nine-alarm fire that tore through part of a block in Dorchester’s Lower Mills neighborhood this weekend destroyed or severely damaged five houses assessed at nearly $3 million. However, had the fire occurred merely five years before, the same properties would be worth only $1.91 million, according to city of Boston assessment records.

Authorities said the fire started at a vacant multifamily property at 39 Old Morton St. before spreading to homes to its left, right and rear. At least five buildings, including at least one multifamily building, were rendered uninhabitable or completely destroyed, according to photos posted on Twitter by the Boston Fire Department.

According to data from The Warren Group, publisher of Banker & Tradesman, the median single-family sale price in Dorchester for all of 2014 was $360,000, while the median condominium price was $305,000. By 2018, those figures had grown to $558,500 and $475,500, respectively.

The Boston Fire Department tweeted that the cause of Saturday evening’s nine-alarm fire is currently unknown. The department said seven firefighters and two civilians were hospitalized with non-life-threatening injuries.

The fire started at around 4:45 p.m. and the ninth alarm was struck around 45 minutes later. Firefighters were still on the scene checking for hot spots around 10 p.m.

Material from the Associated Press was used in this report.