SURFSIDE, Fla. (AP) — An engineer hired to help figure out why a South Florida condominium collapsed last month is warning officials that it still might not be safe enough to reopen the avenue out front.

Structural engineer Allyn Kilsheimer warned officials in a letter on Thursday that Collins Avenue could crumble.

All that remains of the Champlain building are the walls of the underground parking garage around a hollowed-out foundation.

He says that traffic could cause the nearby wall to fail and parts of the street to collapse. Miami-Dade officials say they’ll shore up the walls before fully opening the main thoroughfare for beachfront cities.