(CNN) -- About 1,500 tourists were evacuated Tuesday from the Sagrada Familia church, a popular destination for visitors to Barcelona, Spain, after a man set a fire inside, authorities said.
The fire occurred in the church's crypt, a section always open and used for religious purposes. It caused no injuries and unknown damage to the crypt, authorities said.
Investigators arrested the man, a municipal spokeswoman said.
The church is closed to the public and will open when it is deemed safe to visit, the spokeswoman said.
The Sagrada Familia, or "holy family" church, is still under construction after more than 100 years. It was designed by Antoni Gaudi, an architect well-known for many buildings he designed in Barcelona. Only one tower and most of one facade at the church had been completed by the time he died ni 1926.
Gaudi planned the church to have 18 towers -- 12 for the apostles, four for the evangelists, one for the Virgin Mary and the tallest for Jesus.
Jordi Fauli, the deputy architect, said the privately-financed work may be done by 2026, on the 100th anniversary of Gaudi's death.
Asked once why it was taking so long to finish the Sagrada Familia, Gaudi replied, according to his assistants, "My client -- meaning God -- is not in a hurry."