Lawyers for survivors of the capsized Costa Concordia cruise ship on Saturday pressed for new drug tests on the ship's captain after traces of cocaine were reportedly found on the outside of a hair sample.

But the consultant who did the analyses for prosecutors stood by results, which found no presence of the drug in urine samples or within the hair of Capt. Francesco Schettino.

Italian consumer protection group Codacons is representing some survivors of the shipwreck of the cruise liner, which rammed a reef near a Tuscan island the night of Jan. 13. Under Italian law, those attaching civil suits to a criminal case must be informed of, and allowed to monitor, evidence and other developments in the probe.

Codacons said Saturday that some traces of cocaine were found on a hair sample and in an envelope containing the sample, but noted that a urine sample taken from Schettino and an analysis of the hair itself found no presence of the drug. It called that finding "very strange" and said it had asked prosecutors on Friday to order new testing to see if the samples might have been contaminated.

Capt. Francesco Schettino, seen in this undated file photo, has been held under house arrest while he is investigated for alleged manslaughter and abandoning his ship. (Reuters)

The Italian news agency ANSA quoted the forensic medical expert who carried out the toxicology test as dismissing Codacons' concerns about the external trace of cocaine.

The expert, Marcello Chiarotti, was quoted as saying the modest trace of cocaine "was a marginal problem that absolutely doesn't invalidate the results of the analysis" that found none of the drug inside the hair itself or in the urine. Traces of cocaine in the urine or inside the hair itself would have pointed to consumption.

The prosecutor's office in Grosseto, Tuscany, was closed Saturday, as was the law office of the attorney defending Schettino, who is under house arrest in his home near Naples while he is investigated for alleged manslaughter, causing a shipwreck and abandoning his ship. The lawyer could not be reached by cellphone.

But ANSA quoted the lawyer, Bruno Leporatti, as saying the test results yielded nothing new. "We have always been sure that Schettino didn't take drugs," the Grosseto-based lawyer was quoted as saying.

'There can be problems like this'

Schettino has denied abandoning ship and insisted the reef was not marked on navigational charts.

Thirty-two people are believed to have perished, including 15 whose bodies have not been found.

Chiarotti was described as expressing confidence in the results. "We will be able to clear this problem up later," ANSA quoted him as saying. "Those who work in our field know that there can be problems like this." He told ANSA that "the results leave no doubt," adding that he would formally hand in the report to prosecutors next week.

Chiarotti is on the teaching staff of Rome's Catholic University of the Sacred Heart. The university said he was not in his office Saturday.

ANSA, without citing sources, said that traces of the drug might have resulted if Schettino's hair had come in contact with someone who had handled cocaine.

A Codacons spokesman, Stefano Zerbi, told the Associated Press that the group was raising the possibility with prosecutors that the samples might have been poorly preserved. Codacons' statement said the results indicate a "strange, passive contamination," in which cocaine somehow got onto Schettino's hair even though he wasn't using the drug.

The samples were taken on Jan. 17, Codacons said.

The consumer group on Friday also asked prosecutors to order DNA testing of the samples to confirm they are indeed those of Schettino, to eliminate the possibilities the samples were accidentally mislabeled or switched.

The Concordia's hull was speared by the reef after the ship cruised close to the island of Giglio in what many contend was a publicity stunt.

The Concordia was carrying some 4,200 passengers and crew on a week's cruise on its standard route when it crashed into the reef during dinner a couple of hours after leaving an Italian port.