Boston firefighters are battling a blaze that has engulfed at least two houses in Dorchester, reaching 6-alarm status.

“A 6th alarm has been ordered as companies continue to battle the intense flames and try to stop the fire from spreading to more homes,” the Boston Fire Department tweeted at 4:20 p.m. following other tweets that described the scene: “Thick black smoke fills the sky as the fire continues to burn.”

The department first noted the fire in the rear of 21 Ellington St. in Dorchester about 20 minutes earlier in a tweet that noted the fire had jumped to the neighboring home at 19 Ellington St. and that the department had struck two alarms.

The intensity of the situation quickly escalated over the intervening minutes, rising to 6 alarms at 4:20 p.m.

Ten minutes later, at 4:30 p.m., the department stated the fire had been knocked down.

Reporter Flint McColgan contributed to this report. This is a developing story.