UPDATE: Pierce Crowley was found safe in New York City in the early-morning hours of May 31. 

Hundreds of volunteers have joined the search for teenager Pierce Crowley, who has been missing since Friday, May 25. Celebrities have joined the effort as well, utilizing their social media networks to spread the word about the missing boy from Westchester, N.Y.

Designer Tory Burch, singers Mike Posner and Sammy Adams, E! Network's Jonathan Cheban, Ray Rice of the Baltimore Ravens, Josh Bush of the New York Jets and Real Housewives of New Jersey cast member Albie Manzo have all tweeted out the hashtag #findpierce to help find Pierce Crowley.

Many Twitter users have tweeted to the Kardashians, including Kim and Khloe, to join in the movement to find Crowley. Kim Kardashian alone has almost 15 million Twitter followers and over 9.1 million Facebook likes. She posted the missing person's flier, with three photos of Crowley, on her official Facebook page.  She also retweeted a link to Crowley's poster on Twitter. 

The Harvard Alumni Association tweeted out a message to Harvard alumni, asking them to help search for Pierce Crowley. Pierce's father, Peter Crowley, graduated in the class of 1981.

The boy's friends started a social media push to further publicize the story and get more people involved. A Facebook page and a Twitter hashtag, #findpierce, were created to disseminate updated information on the case.

My birthday is tomorrow and my biggest birthday wish is for my friend Pierce Crowley to return home safely...We miss you kid #FindPierce, tweeted @AnttCee

Crowley, a freshman at Iona Preparatory School, was last seen on Friday, May 25. According to a News 12 Westchester report, the boy left New York-Presbyterian Hospital in White Plains, where he was enrolled in a program, with a friend on Friday and went to The Cheesecake Factory on Bloomingdale Avenue. The two later took a taxi to the White Plains Metro-North train station where they parted ways. Crowley was last seen in the cab, reported the Nyack-Piermont Patch

FOX News reported that police are now searching for the cab driver who drove the boy to the train station. 

Crowley stands 5-feet, 10-inches tall and weighs 150 pounds. He was last seen wearing a bright blue Florida Gators short-sleeve T-shirt. He was last seen in the area of 21 Bloomingdale Avenue in White Plains, N.Y.

Speaking to CBS Local news, the boy's mother, Gretchen Crowley, said, Our family loves and misses Pierce and we are very worried for him ...The last four days and four nights have seemed like an eternity.

His father, Peter, added: Pierce needs to know how much his family and friends love him. He needs to know people just want him home safely. He's not in any trouble.

Family friend Peggy Dunne said, [Pierce] is a charming, talented, bright student and an amazing athlete ... His family and his friends are just totally distraught about him missing. Dunne warned those looking to help the Crowley family to be wary of fundraising propositions, as no legitimate fundraising operation has been set up yet.

Anyone with information about Crowley's disappearance is asked to contact the White Plains police at 914-422-6111. The family have also set up an email address findpiercecrowley@gmail.com.  All volunteer inquiries can be directed to Dunne, at dunnepd@aol.com.