Some visitors to the Toronto Zoo recently got a little too close to one of the giant pandas.

Late Sunday afternoon, some children and adults got into an off-limits area, coming within a few centimetres of a panda on the other side of a chain-link fence. A cellphone video of the incident appears to show some of the visitors sticking their fingers through.

The bears may look harmless, but zoo spokeswoman Jennifer Tracey said there are barriers around them for good reason.

Da Mao is one of the two giant pandas living at the Toronto Zoo for a five-year period. (CBC)

"They are bears, they are dangerous," she told CBC News in an interview.

The zoo says the door leading to the area was left unlocked and its padlock was not where it was supposed to be.

"The padlock was definitely not on the door, however the door was closed," said Tracey.

The zoo is now investigating how that happened. That process will involve speaking to staff.

Tracey said zoo staff had last seen the door closed at 5:15 p.m. that day. But the zoo didn't know about the problem until 5:42 p.m.

The zoo is hosting two giant pandas for a five-year period, after which they will spend another five years in Calgary.

Those pandas, Da Mao and Er Shun, arrived in Toronto in March last year, amid much fanfare. They flew to Canada on board a FedEx plane and were greeted by Prime Minister Stephen Harper at Pearson International Airport.

Their arrival marked the first time the Toronto Zoo had hosted pandas in nearly 30 years.

The panda incident comes just three months after some high school students hopped a fence so that they could take a picture near Humphrey, a young polar bear who was born at the zoo last year. The zoo investigated that incident, too.