A Hello Kitty theme park in western Tokyo was forced to temporarily close on Saturday after receiving what it labeled a "terrorist threat."

Sanrio Puroland in Tama notified police around 9 a.m. that it had received an email warning a "hazardous" object had been placed on the premises. The email arrived on Saturday, according to the theme park.

File photo taken August 2008 shows the main entrance of Sanrio Puroland in Tama, western Tokyo. (Kyodo)

"We will temporarily close today, because we cannot fully ensure the safety of customers, cast and on-site staff," Sanrio Puroland said on its website.

The police said they have searched the area, but nothing suspicious has been found so far.

The indoor theme park featuring Hello Kitty and other Sanrio characters opened in 1990.