BROOKLYN - Fire officials believe children playing with matches started a fire on Willoughby Avenue Friday that injured seven people, four of them critically.

The early morning fire trapped a mother and her three children in the house as it burned. One firefighter and several residents were injured.

The fire was contained to the structure and did not spread to other brownstones on the street. The incident has raised questions about why the children were possibly left unsupervised and playing with matches.

Officials say the mother and children were taken to Woodhull and Cornell medical centers for treatment.