Passengers 'boiled alive' on heated buses
Passengers have complained of being "boiled alive" on buses - after heaters were switched on during the hottest day of the year.
One passenger thought she was going to "pass out" and another said it felt like he was "walking into an oven".
One man said the driver told him the heating needed to be on in order to keep the engine cool.
The services are run by East Midlands bus operator Trent Barton, which said it was not aware of the problem.
Tom Morgan, director of service delivery, said: "Our vehicles are one of the most modern fleets in the country and we don't need to put our heaters on to cool our engines down."
Mr Morgan said he would need to find out more in order to explain what happened.
Rainu Bhele said fans on the Mickleover service in Derby were blowing out "very hot air" and estimated that temperatures reached between 35C (95F) and 45C (113F).
"I've been to India in 46C heat and it felt very similar," she said.
"It was significantly cooler outside when I got off the bus, which is saying something."
She said she felt quite dizzy and lightheaded by the time she got home.
"It was awful. I thought I was going to pass out and there was no way of cooling myself down," she said.
Temperatures reached 32C (90F) across Derbyshire and Nottinghamshire on Tuesday, which was the hottest day of 2016 in England and Wales.
'Heating on full blast'
John Heath, who took a service between Nottingham and Mansfield on Tuesday, said passengers were "boiled alive".
"It was like walking into an oven," he said.
"The windows were open in the bus but made no difference because the heating was on full blast."
Mr Heath said he spoke to the driver when he got off.
"He said 'Sorry mate I can't turn it off, it's on all the time, it helps the engine'," he said.