VALLETTA (Reuters) - Maltese investigators believe a man charged with murdering an anti-corruption journalist set off the car bomb which killed her via SMS from a cabin cruiser out at sea, police sources said on Wednesday.

Three men were charged on Tuesday over the death of Daphne Caruana Galizia, whose car was blown up as she drove out of her home on Oct. 16. The crime shocked the Mediterranean island and raised concerns among European Union lawmakers about the rule of law there.

The three, named as Vince Muscat, and brothers Alfred and George Degiorgio, have all pleaded not guilty.

Police sources said investigators suspected George Degiorgio sent the text message after receiving a signal from his brother Alfred, who they believe acted as a lookout. A boat has been impounded. There was no immediate statement from the men’s lawyers.

Caruana Galizia wrote a popular blog which highlighted cases of alleged graft and targeted politicians in government, including Prime Minister Joseph Muscat, and the opposition.

Seven other men were arrested in connection with the probe and then released without charge, police said. Caruana Galizia’s family, which has criticized the handling of the case, said in a statement on Wednesday that the murdered journalist had not been investigating any of the 10 people arrested.

Simon Busuttil, former leader of the opposition in the Maltese parliament, tweeted a link to the statement, adding: “This can only mean that those who commissioned the assassination of #DaphneCaruanaGalizia are still out at large.”

Evidence gathered so far suggests the bomb was placed inside her rented car while it was parked in an alley outside her house six miles from Valletta on the night before her death.

Mobile phones were recovered from the sea in Marsa, an inland area of Valletta harbor, the sources said.

Prime Minister Muscat has called the killing an attack on press freedom, and asked the U.S. Federal Bureau of Investigation to help local police investigate. Caruana Galizia’s son said she was killed because of her work.

Members of an EU fact-find mission said last week there was a “perception of impunity” in Malta.