Havana, Cuba (CNN) -- Leading Cuban dissident Oswaldo Paya Sardinas was mourned Monday amid conflicting accounts of the car crash Sunday that took his life.
"Paya gave decades of his life to the nonviolent struggle for freedom and democratic reform in Cuba," read a statement issued by White House spokesman Jay Carney. "He remained optimistic until the end that the country he loved would see a peaceful and democratic transition."
A devout Catholic, Paya, 60, headed the Christian Liberation Movement, which attempted to carry out political change in Cuba through non-violent means, often using the legal framework of Cuba's socialist system.
On Monday, the state-run newspaper Granma featured a short item on the car crash that took Paya's life but did not detail who he was or his work as a leading critic of the island's leaders.
The article's headline called the accident as "regrettable."
Anti-government activists rarely are reported on by Cuba's state-run media, except to call them "traitors" working in the employ of the U.S. government against their countrymen.
According to a statement about the crash issued by the Cuban government late Sunday, the unidentified driver of the car lost control and struck a tree near the eastern Cuban city of Bayamo.
On Sunday, Paya's daughter, Rosa Maria Paya, told CNN that her family believed a second car had struck the vehicle her father was traveling in, forcing it off the road.
Cuban Harold Cepero also died from the crash. Two others were in the car, it said: Swedish citizen Aron Modig and Spaniard Angel Carromero, who suffered injuries from the impact.
Carromero, a technical adviser to the city of Madrid, received a gash on his head but he and Modig had been released from the hospital in Bayamo, said Francisco de Borja Morate Martin, a counselor in the Spanish Embassy in Havana.
Spain's consul to Cuba had traveled to Bayamo to assist Carromero, who was being interviewed by Cuban police, Morate said.
It was not clear where the men where traveling when the crash took place. The two survivors' testimony could be key to understanding how the crash occurred.
According to the Cuban government's statement, the crash is under investigation by police.
In 2002, Paya delivered to Cuba's National Assembly petitions containing 11,020 signatures calling for democratic elections and freedom of speech.
Paya called the proposal the Varela Project, in honor of a Cuban priest who had battled against Spanish colonial control of the island.
The Varela Project did not lead to changes to Cuba's one-party system. Instead, the Cuban government responded with its own petition drive that permanently ratified the socialist nature of the island's government.
During his 2002 visit to Cuba, former U.S. President Jimmy Carter was permitted to speak on Cuban state television and mentioned the Varela Project, the first time that many Cubans had heard of Paya's efforts to change the country's political system.
Memorial services were being planned for Paya in Havana, Miami and Madrid.