Police are investigating separate incidents in which two 15-year-old girls said they were abducted in Mililani Wednesday morning, including one case in which the girl told police she was sexually assaulted.

Maj. Clayton Kau, Honolulu Police Department spokesman, yesterday said investigators were trying to determine if the abductions were related. Both girls described their assailant as a male in his late teens or early 20s, but police did not release any further information.

"Because the investigation is still ongoing, we're trying to ensure that whatever information we do gather, we confirm it," Kau said.

In the first incident, the girl told police that a male threatened her with a knife and held her against her will at about 3:30 a.m. Police said the girl managed to escape after the suspect was confronted by a witness.

At about 7 a.m., the second victim said she was walking to a friend's house when she was abducted and sexually assaulted by a male driving a white van.

Police did not provide locations of the abductions.

Kau cautioned residents, particularly teenagers, to be cautious when they're going out.

"Go out in groups, walk in well-lit areas and call 911 to report suspicious activity," Kau said. "It is important for people to be mindful when they're out and about."

Officials at Mililani High School yesterday issued notices to students and parents about the incidents.

Principal John Brummel said he did not receive any reports that the victims are Mililani High students, but the school sent an automated voice-mail advisory to parents as a precaution. He said an announcement also was made over the school's public address system yesterday to warn students to be aware of strangers and of their surroundings .

"We indicated we didn't want any type of panic so we let them know that we did not know if they were Mililani High School students, but we're concerned about the safety of everybody in the Mililani community and that's why we sent the announcement out," Brummel said.

Mililani High has an enrollment of 2,500 students in grades nine through 12. Brummel said he hopes his students will take the warning to heart.

"Maybe at one time Mililani was a safe community, but even at Yale with that situation with that young lady (murder victim Annie Le), it kind of tells you of the world that we live in today and not to take things for granted," he said.

"So be cautious and make sure you're with somebody else and be aware of everything."

Police ask that anyone with information on either of these cases call police at 911.