Organizers of a renovation project on the Gateway Arch grounds in St. Louis say the opening of a museum and expanded visitor center will be delayed until summer 2018.

The Gateway Arch Park Foundation on Tuesday announced that the Museum of Westward Expansion and the expanded visitor center won't be completed by the end of this year as expected.

Ryan McClure, spokesman for the foundation, attributed the delays to unforeseen problems with construction underground, where the museum is located. Problems included delays in building a tunnel and obstacles with existing utility lines.

The museum and visitor center are the last major pieces of the $380 million project, which began in 2013.

The Arch, a new store and the ride to the top of the Arch are currently open.