Saudi Arabia Civil Defense said that in the early hours of Saturday, an early warning system was activated in two districts, al-Kharj and Yanbu, and asked residents to stay indoors in buildings and move away from windows and open areas.

Hours later, the agency announced that the danger had been lifted, but did not disclose the nature of the threat.

The warning was issued shortly after a U.S. official told the website Axios that the Islamic Republic launched a ballistic missile toward a U.S. military base in Saudi Arabia. This was the first direct attack on Saudi soil in the past four months.

Al-Kharj is the location of facilities and military bases. Yanbu is the main export terminal for Saudi oil via the Red Sea and along the East-West pipeline route, which reduces the need for the Strait of Hormuz for exports.