Two 15-year-old high school students were arrested on suspicion of preparing to carry out a school shooting at Corona High School in California, the City of Corona Police Department said in a statement on Tuesday.

Authorities said the investigation into the alleged plot began in early October after the FBI alerted local police to social media threats.

“A collaborative investigation led to the immediate arrest of a 15-year-old female Corona High School student,” police said in the statement, with subsequent enquiries leading to the request of a second 15-year-old female student who attended Norco High School.

Police said that the two suspects “spent several months researching school shootings and discussed how they could carry out a potential attack at Corona High School on an unspecified future date.”

“Communications showed the suspects discussed methods to obtain weapons but had not yet been able to do so. No weapons were located during the searches,” the statement added.

The two suspects remain in custody on charges of conspiracy to commit murder, police said, with the investigation ongoing “in close partnership” with the FBI.

FBI Director Kash Patel said in a statement that “a potential act of targeted violence against a Southern California high school was disrupted before anyone was harmed.”

“There is no greater priority than protecting our kids, and threats against our schools will be met with the full force of the FBI and our partners,” Patel added.