Police are searching for a group of four men and one woman believed to be responsible for multiple violent robberies on the J train this month. The incidents happened over the course of one weekend, starting Friday afternoon, May 8th. According to investigators, the victims were threatened with knives and, in some cases, punched in the face.

On Friday around 2 p.m., a 25-year-old woman was on the J as it approached the Jamaica Avenue and 121st Street station when a man pulled out a knife and forced her to hand over her cash and MetroCard. The NYPD says he immediately fled the train "to parts unknown."

Shortly before 2 a.m. early Sunday morning, an 18-year-old was riding a northbound J train approaching the Jamaica Avenue and 111th Street station when four young men and one woman brandished a knife and punched him in the face. They then tore off his Jordan sneakers, Gucci belt, and stole his iPhone 6 and a shopping bag with a jacket in it.

A few minutes later, a 47-year-old man was watching a movie while riding the northbound J train as it approached the Fulton and Cleveland Street station. A young man in his 20s walked up to the victim and demanded his cell phone. When the victim refused, the suspect punched him in the face while a second suspect brandished a knife. The first suspect then grabbed the suspect's iPhone 5 and fled the station, while the other (identified by police as Suspect #2) remained on the train.

None of the victims' injuries required hospitalization. The suspects remain at large; here's how the NYPD is describing them:

Suspect #1 is described as a male Black, in his 20's, with dreads, wearing a black hooded sweater.

Suspect #2 is described as a male Black, in his 20's, wearing an orange t-shirt.

Suspect #3 is described as a male Black, in his 20's and approximately 6'2" tall.

Suspect #4 is described as male Black, in his 30's, approximately 5'4" tall and 140lbs.

Suspect #5 is described as a female Black and carrying a black jacket concealing the knife under the jacket.

Anyone with information in regards to this incident is asked to call the NYPD's Crime Stoppers Hotline at 800-577-TIPS. The public can also submit their tips by logging onto the Crime Stoppers Website or texting their tips to 274637(CRIMES) then enter TIP577.