The CEO of the Toronto Transit Commission issued a rare apology Tuesday via YouTube, to explain service delays that plagued Monday's evening commute.

"I just want to say sorry for the poor subway service we offered last night," Andy Byford said in the video. He also alluded to new service improvement commitments promised last month in a customer charter and admitted "clearly, we didn't meet that objective last night."

The delays, which included waits for trains that exceeded 20 minutes at some stations, prompted TTC spokesman Brad Ross to issue a Twitter message Monday evening saying the delays were "unacceptable."

The problems subway commuters faced on Monday's evening commute included:

• Dupont Station: 24 minutes. At about 6 p.m. a train's doors opened while it was inside the tunnel. Ross said this was a result of "human error." Once it happened, staff had to turn off track power and check all sides of the train and return it to the station. “At the height of rush hour, that is a considerably long delay,” Ross told CBC News.

• Eglinton Station: 15 to 17 minutes. A fire at track level delayed trains, this time on the Yonge-University-Spadina Line. These fires are commonly caused by debris, often newspapers, left inside the station and blown onto the track by passing trains.

• Keele Station: About 10 minutes. Another track-level fire. This one cleared quicker than the one at Eglinton.

• Passenger service alarms. The TTC dealt with a number of these on Monday afternoon, which led to further delays.

Byford offered an explanation in the video released Tuesday, saying the doors opened at Dupont Station "while the train was stationary by a staff member. And clearly, we're looking into how that could have happened."

Ashley Botting, who was on the train when the doors opened, told CBC News the passengers were shocked.

She said the car stopped unexpectedly — and the doors opened.

'If it were a packed subway, someone would've fallen off.'—Ashley Botting, who was on the TTC train when the doors opened

"If it were a packed subway, someone would've fallen off. Absolutely. I mean the chime did happen before, but, you know, normally you're just wedged up against [the doors]," she said.

After a couple of minutes of silence, the doors closed, Botting said.

It's not the first time this has happened.

In April 2000, a TTC worker was disciplined after two cars sped along a tunnel with the doors open.

And in May 2000, a subway train was leaving Kennedy station at 5 km/h when the doors opened and closed for two seconds. A guard had opened the doors in error, the TTC said in a 2000 news release.

Communication about delays needs improvement: TTC

Byford also said the lengthy delays were due to the two fire alerts, as the evening commute was hitting its peak.

"Now in such circumstances, we put safety first. We don't take any risks," he said.

Services were suspended until Toronto Fire Services gave the TTC the all-clear to resume, Byford said.

The doors on a TTC train opened while it was still in the tunnel near Dupont Station. (Ashley Botting/Twitter)

He also acknowledged that passenger alarms at the same time added to the delay.

Ross said part of the problem on Monday night was communicating the delays to passengers, who are often unable to hear the announcements inside crowded trains.

‘We need to do a better job of making sure the announcements on board the train are clear," he said.

Monday's problematic commute comes less than a month after the TTC announced a customer charter, a series of 30 promises aimed at improving service and keeping customers informed about service delays.

"The key to that improvement is increased reliability and punctuality of the service," said Byford on Tuesday. "And clearly, we didn't meet that objective last night. So once again, I am sorry for the delays last night, and I appreciate it was a frustrating trip home."

With files from CBC's Linda Ward