A double-decker OC Transpo bus that caught fire in rural Ottawa Tuesday morning with 70 to 80 passengers on board was performing sluggishly just before the blaze, and had been involved in a crash in 2013.

The fire happened on Piperville Road, between Anderson Road and Farmers Way in southeast Ottawa, at about 6:50 a.m. ET.

Troy Charter, OC Transpo's director of transit operations, said the bus operator did everything right. (CBC News)

The bus was servicing Route 222, heading east along Piperville from the community of Vars to downtown Ottawa.

While driving the route the bus operator noticed the bus was "sluggish," and called OC Transpo's transit control centre to report it, according to Troy Charter, OC Transpo's director of transit operations.

The driver was told to pull over in a safe area and check it out, but saw nothing when he walked around the bus, Charter said at a news conference Tuesday afternoon.

After getting back on the bus, everyone heard a loud "bang, or a pop," Charter said, followed by the appearance of smoke and flames.

Everyone made it out safely.

Bus involved in previous incident

The same bus, No. 8010, was involved in a crash in April 2013.

It was heading south along Woodroffe Avenue when it went off the road in icy, slushy, windy conditions and slammed into a hydro pole, knocking out power to thousands of people.

The driver was the only person inside. He wasn't injured.

"The bus has been in service then, reliably in service since then," Charter said. "I don't have any indication to think it is related, but I don't want to speculate, either. It's too early to tell at this point."

A "thorough root cause analysis" will be performed in the coming days, he added.

The bus was purchased in 2012, Charter said. It's one of 117 double-decker buses that each cost nearly $1 million and were manufactured by Alexander Dennis, a company based in Scotland.

The same bus was involved in a crash on Woodroffe Avenue in 2013, seen at the left. (CBC News)

'Heard an explosion'

Passenger Ewa Roy told CBC News people heard a loud noise and started seeing smoke after the bus pulled over early Tuesday morning.

"We heard an explosion, and we assumed that it was a tire that exploded. And then there was some smoke that started coming out from the back end of the bus," she told Radio-Canada in an interview later Tuesday morning.

Bus passenger Ewa Roy says OC Transpo bus passengers heard an explosion and started seeing smoke coming from the back of the bus early Tuesday morning. Everyone managed to get out safely and calmly. (Radio-Canada)

"And we all came out very calmly, everybody was very calm. We were surprised when the explosion happened, but then after that we all just calmly left the bus and ended up in the parking lot of the park and ride.

"There was a lot of smoke at first, and then the flames started. Firemen came within maybe 15 minutes, then the other bus came around 25 minutes later and picked everyone up."

The drama was mainly visual, she said.

"It is a little bit scary at first, but we were fine, everybody was fine, and that's what matters, really. Everyone's safe. … I commend the bus drivers and my [fellow passengers]. Everybody kept calm and it was all right," Roy said.

Double-decker this morning caught fire! <a href="https://twitter.com/hashtag/OttNews?src=hash">#OttNews</a> <a href="https://t.co/T3HpVNdAQY">pic.twitter.com/T3HpVNdAQY</a> —@peteroy15

No one injured

The bus driver used a fire extinguisher but wasn't able to suppress the flames, Charter said, adding that he did everything he was supposed to.

By the time Ottawa firefighters arrived, the bus was engulfed in flames. It took about 10 minutes to get the fire under control, according to the fire department.

No one was injured.

Piperville Road was closed from Anderson to Farmers Way but has since reopened.

Here's what the entrance to the bus and the driver's seat looked like after the fire. (Roger Dubois/CBC)