Tokyo ? The U.S. Navy is investigating whether an American sailor was involved in the slaying of a 56-year-old Japanese woman, police and diplomatic sources said Thursday, putting the spotlight once again on Japan’s uncomfortable relationship with the massive U.S. military presence on its soil.

Yoshie Sato was found dead shortly after 6:30 a.m. Tuesday in the entrance to a commercial building in Yokosuka City, a port 43 miles south of Tokyo and home to the largest American naval base outside the U.S. She had been beaten and died from internal bleeding, according to Japanese police, who said her empty wallet found nearby suggested robbery was the motive.

Sato’s death has the potential to inflame feelings here against the approximately 47,000 U.S. troops stationed in Japan, along with roughly 14,000 sailors with the U.S. Seventh Fleet who spend about half the year in port at Yokosuka. Tokyo is under intense domestic pressure to close – or at least downsize and relocate – U.S. bases that are heavily subsidized by Japanese taxpayers.