Sources at Turkish attorney general’s office told Al Jazeera samples of acid were found at Saudi envoy’s Istanbul home.

Saudi authorities used acid and other chemicals to dispose of slain journalist Jamal Khashoggi‘s body, a source at the Turkish attorney general’s office has told Al Jazeera.

The source said traces of hydrofluoric acid and other chemicals were found in a well at Consul General Mohammed al-Otaibi’s home in Istanbul.

Al Jazeera’s Andrew Simmons, reporting from Istanbul, said on Thursday that Turkish investigators were able to take samples from the well when they were first granted access last month.

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“We know that on the night of October 16 to 17, when the Turkish investigators were working inside the residence and wanted to gain full access to the garden and the well shaft, they were not given permission […] but were able to briefly take some samples from it with rods from the top of it,” he said.

“Those samples have been processed and they include proof that there had been hydrofluoric and other chemicals.”

Simmons said the other samples taken from the sewerage and drainage system around the diplomatic district also showed the use of acid.

Saudi Arabia had consistently maintained that Khashoggi left the consulate building after obtaining the necessary paperwork that would allow him to marry his Turkish fiancee before admitting to the journalist’s killing on October 20.

It has since provided conflicting accounts about the way in which Khashoggi was killed.

In a meeting with US evangelicals on November 1, Saudi Crown Prince Mohammed bin Salman reportedly reiterated promises to get to the bottom of Khashoggi’s killing and punish those responsible.

According to the delegation’s organiser, quoted in an article published on Axios news site on Thursday, 18 people had been arrested and five sacked in connection with the killing.

‘Cover-up team’

On November 2, Yasin Aktay, a close aide to Turkish President Recep Tayyip Erdogan, said he believed Khashoggi’s body was dissolved in acid.

“The reason they dismembered Khashoggi’s body was to dissolve his remains more easily,” Aktay said.

“Now we see that they did not only dismember his body but also vaporised it.”

A few days later, the pro-government Sabah newspaper reported that Saudi Arabia sent a chemist and toxicology expert to Istanbul in an attempt to cover up evidence of the killing.

According to the Turkish daily, Riyadh sent an 11-member “cover-up team” on October 11, nine days after the Washington Post columnist vanished.

The paper said chemist Ahmad Abdulaziz al-Janobi and toxicology expert Khaled Yahya al-Zahrani were among “the so-called investigative team”, which visited the consulate every day until October 17, before leaving Turkey on October 20.