By David Salazar ( | First Posted: Jan 11, 2013 12:11 AM EST

A candle with a photo of Jenni Rivera are seen outside Arena Center in Monterrey (Photo : Reuters)

Relatives of the four passengers who died alongside Jenni Rivera have filed a lawsuit against Rivera's company and the owners of the aircraft.

The family members allege that owners and previous owners of the aircraft were negligent of the plane's poor condition but also that an additional and unidentified group of people practiced negligence in not only maintaining the 43-year-old jet but also repairing it, according to USAToday.  They also insisted that the two pilots on board were probably not qualified to fly the aircraft.

"We are trying to unravel the mystery of how this came to be. Who selected this plane, what condition was this plane in and how did these pilots get behind the stick of this aircraft?" said Paul Kiesel, the plaintiffs' attorney.

He added, "It is hard to imagine an explanation of why a plane flying at 28,000 feet simply dropped out of the sky (without) some significant act, probably of gross negligence."

The 22-page lawsuit indicates that the plane's engine was built in 1969 and was often referred to as a "bag of bolts." The document also asserts that the jet hit a runway marker in a Texas airport and suffered "structural damage."

The accident happened on Dec. 8 after Rivera, known as "La Diva de la Banda" performed a concert in Monterrey. According to the NY Daily News, the plane lost radar contact just 10 minutes after it took off and crashed into a rough mountain terrain in northeastern Mexico. The other people killed in the crash alongside Rivera included publicist Arturo Rivera, make-up artist Jacobo Yebale, attorney Mario Macias Pacheco and hair stylist Jorge Armando "Gigi" Sanchez Vasquez. The pilot and co-pilot also died.

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