MONTREAL -- A federally-appointed panel of scientists will study Montreal's plan to dump eight billion litres of sewage into the St. Lawrence river.

Environment Minister Leona Aglukkaq made the announcement on Sunday.

Environment Canada says the city did not provide enough data to conclude whether or not the untreated wastewater would be "acutely toxic."

The three scientists have until Nov. 2 to complete their analysis, which will include assessing environmental risk and looking at alternative options.

The city had planned to close a major sewer to do maintenance work until Ottawa ordered a temporary halt to the project last week.

Montreal's mayor has described the federal actions as unreasonable and inappropriate and has said delaying the project could cause bigger problems.

In a letter sent to Aglukkaq on Friday, he noted the federal Environment Department has been aware of the city's plan since September, 2014.