Two children have been found to have high levels of lead in their blood in tests conducted after the Notre-Dame fire, according to health officials.

Another 16 are considered to be borderline and require monitoring, they said.

Critics have accused authorities of acting too slowly to protect workers and residents from lead pollution.

In all, some 175 children have been tested due to concerns over potential poisoning in the wake of the April 15 blaze in which hundreds of tonnes of lead melted and some entered the atmosphere as dust.

Authorities in June recommended blood tests for children under seven and pregnant women who live near Notre-Dame as they are especially vulnerable to health problems from lead poisoning and exposure.

Paris' regional health agency, ARS, said that of the two worst cases, the first had been known for some weeks and doctors believe the high levels may be linked to lead in the family home’s balcony.

The second child goes to a school near the cathedral that was closed in July due to high lead levels found on its grounds.

The family has been contacted and the child requires regular monitoring but no specific treatment for now, said ARS.