A Spanish official says investigators have detained multiple people in connection with the devastating wildfires on the Canary Islands, but authorities have yet to determine what caused the blazes.

The fires have scorched about 10 percent of the island of La Gomera and were still out of control Thursday morning. Water-bombing planes were resuming flights to douse blazes.

Interior Ministry official Maria del Carmen Hernandez Bento confirmed people had been detained, but did not say how many. She told the Cadena Ser radio station Wednesday night that revealing more information about the detentions could hurt the investigation.

La Gomera is in the Canary Island archipelago off the northwestern African coast. The fires have burned parts of La Gomera's Garajonay National Park, a UNESCO world heritage site.