About 500 Panamanians are believed to have died in the invasion, but rights groups say the true number is higher.
The remains of the 19 victims were initially placed into a mass grave but later reburied in the Jardín de Paz cemetery in Panama City, along with dozens of others.
Some bodies remain unidentified.
Relatives say all the victims of the invasion must be identified so that families can find closure.
“We have been working for 30 years to make sure they have some inner peace,” said Trinidad Ayola, president of an association that is helping to identify the victims.
The government of Juan Carlos Varela has set up a commission to investigate the death toll. Correspondents say the invasion is still a difficult period for many in Panama and there have been calls for 20 December to be an official day of mourning.
The invasion took place on 20 December 1989 after ties between the US government and Panamanian leader General Manuel Noriega sank to an all time low.
Then US President George H W Bush said he was ordering military action to “protect the lives of American citizens” and bring Noriega “to justice”.
General Noriega was arrested two weeks later. He was taken to the US where he was sentenced to jail for drug trafficking and money laundering.
Noriega spent the rest of his life in custody – first in the US, then France and finally under house arrest in Panama. He died in 2017, aged 83, as a result of complications from an operation to remove a brain tumour. (Courtesy BBC)