The blaze in Crumpets Farm Drive, Lytchett Matravers, started at about 11:00 GMT.
Acetylene cylinders were believed to be inside the property and a 70m (230ft) cordon was put in place.
Dorset Fire Service said the A350, which was partially closed, had now reopened. An investigation has started.
Residents whose properties were not affected returned home at 18:00.

Hodgson resigned immediately after England were knocked out of Euro 2016 following a shock defeat to Iceland in the last 16.
Rodgers was named Celtic manager in May after leaving Liverpool in October.
"I've just landed my dream job. The team I've supported all my life," Rodgers said. "I'll be at Celtic, that's for sure."
England under-21 manager Gareth Southgate was installed as the favourite to succeed Hodgson, but he, like Rodgers, has said he is not interested in the job.
Rodgers will be in the Celtic dugout for the first time on Thursday as the Scottish champions take on NK Celje in Slovenia in a pre-season friendly.
Their first competitive action will be in the second week of July against either Estonian side Flora Tallinn or Lincoln of Gibraltar in the Champions League second qualifying round.
"I haven't even walked out for my first game," Rodgers continued.
"Imagine me as a Celtic supporter having walked out on the job at Parkhead!
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"Is it flattering (being linked with England)? It's football. There are very few professions where one minute you're up, then down, then up again - that's just how it goes.
"If people think I can do jobs at a high level, then that's fine. But I'm busy here, worrying about what I have to do here."
Hodgson and the England players have come in for fierce criticism in the wake of the Iceland defeat, and Rodgers believes there will be enormous pressure on whoever is chosen to take the national team forward.
"It's a tough job, England. They've got a lot of good players but there is huge pressure, huge expectancy.
"There is a great group of players there. They've got some wonderful talents in that England squad, but it has been difficult for them at this tournament - and it has been like that for a few tournaments.
"So it's unfortunate how it ended for Roy because he's a good man, a very good coach.
"They now obviously have to appoint someone and look at creating an identity, a way the team can play."

The 22-year-old, who had a loan spell at Rotherham earlier this season, has agreed a deal with the Addicks until the summer of 2019.
Forster-Caskey scored nine goals in 82 appearances for the Seagulls after making his debut aged 16 in 2010.
"Jake is a real talent who has shown his quality in the Championship," boss Karl Robinson told the club website.
Former England Under-21 international Forster-Caskey worked under 36-year-old Robinson last season during two loan stints at former club MK Dons.
He is Charlton's second signing of the January transfer window, and his arrival at The Valley came after winger Ademola Lookman left the Addicks to join Premier League side Everton in an £11m deal.
Meanwhile, Brighton under-23 midfielder Jack Harper has moved to Spanish side Malaga for an undisclosed fee.
Find all the latest football transfers on our dedicated page.
Fifteen residents, including a baby, were evacuated from their homes after a fire broke out in a nearby garage in Dorset.
[NEXT_CONCEPT]
Celtic manager Brendan Rodgers has ruled himself out of the running to replace Roy Hodgson as England manager.
[NEXT_CONCEPT]
League One side Charlton Athletic have signed midfielder Jake Forster-Caskey from Brighton for an undisclosed fee.