ASPEN, Colo. -- Snowmobile rider Caleb Moore remains in critical condition after a crash at the Winter X Games in Aspen and is being closely monitored.

His family thanked Moore's fans for their support Monday and asked for their prayers.

The 25-year-old was performing a flip Thursday when his sled's skis clipped the landing and he went over the handlebars. The snowmobile rolled over him, but he walked off the course with help and went to a hospital with a concussion.

While there, he developed bleeding around his heart and was flown to Grand Junction for surgery Friday. His family said Sunday that Moore then had a secondary complication involving his brain. They didn't provide details.

"Caleb is in critical condition and is being closely monitored," the family said in a statement. "The Moores want to express their gratitude to all of Caleb's fans, friends and family for their strong support and ask for continued prayers in the coming days. The family will not be making any other public statements for the time being. Thank you for respecting the family's privacy during this difficult time."

"Our thoughts and prayers continue to be with Caleb and the Moore family," ESPN said in a statement.

Moore's younger brother, Colten, also crashed in the competition and sustained a separated pelvis.

To help defray the medical costs, a website has been set up for the family. There's a picture of Moore on the site and a message that reads: "Caleb Moore is an inspiration to us all and we want to support him and his family so they may stay strong during this difficult time. If you are not familiar with Caleb, he lives life to the fullest.

"The world knows Caleb as a brilliant freestyle rider, but his family and friends know him as a fun-loving and deeply loyal person."

Information from The Associated Press was used in this report.