More than a week after Hurricane Maria stormed through Puerto Rico, road conditions remain unsafe in many parts of the island and transportation officials are warning that the road to recovery could be long and expensive.

More than 1,500 cases of damaged roads and bridges had been found in Maria’s aftermath, not including problems with a vast majority of traffic signals, Puerto Rico’s transportation chief, Carlos Contreras, said this week.

Contreras said preliminary estimates put the cost for road repairs at $240 million, according to the Puerto Rico news outlet El Nuevo Día.

On Thursday, the Federal Highway Administration issued $40 million in emergency relief to begin work on restoration of critical road infrastructure, including highways and bridges.

All across the island, dangerous debris was being cleared; some residential streets remained impassable because of fallen trees and branches. Emergency crews were being mobilized to rebuild guardrails and traffic signal systems and repair damage caused by mudslides and flooding.

“It is critical to get the island’s infrastructure in working condition as soon as possible so relief supplies and other assistance can be delivered to the people of Puerto Rico,” Transportation Secretary Elaine Chao said in a statement Thursday.

The storm was the strongest hurricane to hit the island in more than 80 years. It disabled radar, weather stations and cellphone towers and knocked down the island’s power grid. Gasoline supplies were low and about one-third of the stations remained closed Friday.

The air traffic control system was so damaged that restoring flight operations remains a challenge. Officials say Federal Aviation Administration crews were continuing to repair radar units, navigational aids and other equipment. As of Thursday, seven of the eight commercial airports were operating on very limited capacity.

Luis Muñoz Marín International Airport in San Juan was operating 32 flights Friday.