A driver claims a chunk of concrete falling from Toronto's Gardiner Expressway smashed into the windshield of her minivan during rush hour on Tuesday.

Ali Saddiqi and his mother, Huma, were driving in separate vehicles underneath the aging expressway Tuesday afternoon. They say they were waiting to make a left-hand turn on Lake Shore Boulevard when concrete from the Gardiner started to crumble.

A piece measuring approximately 30 centimetres in size then crashed into Humas windshield, sending shards of glass all over the front-passenger seat. She was not injured, but was in shock.

"I'm so scared; I closed my eyes," she told CTV Toronto on Wednesday. "I don't know if someone hit me or what happened at that moment."

Her son, whose vehicle was ahead of his mother's, said he heard a "loud bang" and thought two vehicles had collided.

"I look back in my rear-view mirror and I saw the van had the entire windshield smashed in and I saw a couple of pedestrians running over to my mom's car," Saddiqi said.

Police were called to the scene shortly after, and a report to the city was filed.

Saddiqi and his mother said they haven't heard back from the city yet. They have since paid the $300 deductible to repair the shattered windshield.

According to the city, although the freeze-and-thaw cycle can wreak havoc on the already-crumbling Gardiner, it's not clear if the chunk of concrete fell from the expressway.

Officials are investigating the incident, and crews have been sent to ensure the area is safe.

"We do have staff monitoring the Gardiner 24 hours a day," said Coun. Jaye Robinson, who also chairs the city's Public Works and Infrastructure committee. "It's something that we're very concerned about and clearly something the city should have dealt with many years ago."

The city has budgeted nearly $1 billion over a 10-year period to rehabilitate the expressway.

Saddiqi says that may be too long, and is concerned that someone could be seriously injured one day.

"What if it was a kid in a stroller? What if it someone's sunroof was open, arms out of the vehicles? If this was a direct hit to an individual, the trauma would be ridiculous," he said.

With a report from CTV Toronto's Natalie Johnson