The night before he died, Alex Odeh appeared on a local California TV station to talk about the hijacking of an Italian cruise ship, the Achille Lauro, by Palestinian militants, despite warnings from his family that to appear in public at such a tense moment might be dangerous. He made an impassioned plea against terrorism, and said that in the Middle East “we are witnessing that violence breeds violence”.

At 9am on 11 October 1985, Odeh arrived at the offices of the American-Arab Anti-Discrimination Committee (ADC) in Santa Ana, California, where he worked as regional director. As he opened the front door of the premises, a powerful pipe bomb exploded, killing him and injuring seven others.

The FBI immediately declared the murder an act of domestic terrorism, identified suspects and offered a public reward of up to $1m for information that would lead to an arrest and conviction of the perpetrators. But 28 years later, no one has been named, no one has been questioned, and no one has been indicted for Odeh's murder.

Now the ADC and a coalition of other civil rights groups, including the NAACP and prominent members of Congress, have come together to try to kickstart what they see as a moribund investigation. Announcing the new push, Democratic congressman John Conyers, who participated in congressional debates on Odeh's killing in the immediate aftermath, said he was pressing for a meeting with the Department of Justice to try to get justice for Odeh’s widow, Norma, and his three children.

“Twenty-eight years is a long time, and, with all due respect, too long a time,” he said. “We can’t waste any more time over a horrific violent crime that has been on the back burner for far too long.”

In the aftermath of the bombing, the FBI named the Jewish Defense League, JDL, as a focus of its investigations. The league, formed in 1968 by a Brooklyn-based lawyer called Rabbi Meir Kahane, devoted itself to a violent form of anti-Arab Jewish nationalism, and advocated Jews defending themselves “by any means necessary”.

The group was linked to a wave of bombings across the US in the 1980s, and was classified by the FBI as a rightwing terrorist group in the wake of the 9/11 attacks on New York and Washington. According to Rebecca Vilkomerson of the advocacy group Jewish Voices for Peace, some of the original suspects may now be living in Jewish settlements in the Palestinian territory of the West Bank.

One prominent member of the JDL, Robert Manning, has been serving a life sentence since 1994 for carrying out a 1980 mail bombing that killed a woman in California. His name has been linked to the Odeh murder, but he has never been questioned over the case.

Odeh, 41 at his death, was a prominent organiser within the Palestinian American community. He worked for the ADC, the largest Arab American civil rights group, as well as lecturing on Palestinian history and writing poetry. He came to the US in 1972 from Jifna in the West Bank, where he was brought up as a Palestinian Christian, and took up American citizenship the following year.

The relative silence surrounding his death has now been broken, with pressure mounting on the FBI to show more determination in the search for the culprits. In June, Loretta Sanchez, the congressional representative for the 46th district of California, which includes Santa Ana, wrote to US attorney general Eric Holder requesting information on the investigation. “I believe the Odeh family deserves closure,” she wrote.

The Department of Justice responded in July, saying that the case remains open and that the “FBI continues to work to identify any individual(s) associated with the bombing.” It declined to give an update on grounds that the inquiry was still active.

At a press conference on Monday, Sanchez decried the FBI’s response as “unacceptable. The FBI has characterised his death as a domestic terrorist attack, but few details about it are known. The public needs reassurance that all necessary efforts have been taken.”

Benjamin Jealous, the president of the NAACP, likened the Odeh case to that of Medgar Evers, the civil rights activist killed in 1963 in Mississippi. It took 30 years to bring his assassin, Byron De La Beckwith of the White Citizens’ Council, to justice.

Asked why after so many years Odeh’s killers had yet to be indicted, Jealous said that often a “residue of discrimination gums up the wheels of justice in bringing cases to a close. It would be foolhardy to believe that police and prosecutors are all completely immune from the bias of discrimination that leads some people to believe that some lives are worth less than others.”