MONTREAL - The amount of lead in some Montreal tap water is higher than in Flint, Mich., where a lead poisoning scandal seized headlines in the United States, an investigation has found.

The year-long investigation, conducted by more than 120 journalists from nine universities and 10 media groups including The Associated Press and the Institute for Investigative Journalism at Concordia University in Montreal, reviewed thousands of previously undisclosed results and tested water from hundreds of homes in 11 different cities. Researchers recorded lead levels above national safety directives, including at some schools and daycares.

The investigation looked into water testing results over the past 15 years in Montreal and found more than 9,000 cases where lead levels exceeded provincial maximum levels which limit lead concentrations to 10 parts per billion (ppb). 

A duplex built in 1928 in Ahuntsic tested at 72 ppb. A wartime home in Rosemont tested at 60 ppb. 

Researchers suggested the levels may be much higher than tested because municipal workers have traditionally flushed pipes for five minutes before collecting samples. When water is collected directly from the tap, lead levels tend to be much higher.

Based on the investigation, 300,000 Montrealers might have been exposed to lead in their drinking water. 

Mayor Valerie Plante has vowed to test 100,000 homes for lead and speed up the replacement of lead-lined pipes immediately. Public health officials have also stressed Montreal's water is safe to drink, and the contamination is due to outdated pipes in residents' homes. 

The city will foot the bill to replace outdated pipes in homes. Residents will have to pay for replaced piping, but will have 15 years to do so. 

To see if your home is likely to have lead pipes, check here.

In homes that may have some lead pipes, the city recommends filtering water to limit consumption of the contaminant. 

With files from CTV Montreal's Andrew Brennan.