* Rollen returns to work after being released from custody
* Norwegian probe focuses on investment in Next Biometrics
* Norwegian authorities say investigation continues (Adds quotes, details)
By Johannes Hellstrom and Mia Shanley
STOCKHOLM, Nov 7 (Reuters) - Ola Rollen, chief executive of Swedish technology firm Hexagon, denied wrongdoing on Monday and said his conscience was clear after spending more than a week in custody over Norwegian insider trading allegations.
Rollen, who turned Hexagon from a sprawling conglomerate into one of Sweden's most valuable companies, was detained on Oct. 26 and taken to Norway at the request of authorities there on suspicion of insider trading in connection with an investment last year in Norwegian company Next Biometrics ASA.
The investment was made by the Rollen family's private investment firm and did not involve Hexagon.
Rollen, who has not been charged, was released on Friday after spending more than a week in custody.
Returning to work as CEO on Monday, he said he had every intention of continuing to lead Hexagon "with full force". Hexagon will update investors on its strategy and financial plan at a capital markets day in London on Dec. 1.
Speaking publicly about the allegations for the first time, Rollen said he was "truly saddened" by the damage the situation had caused the company and his family.
"But my conscience is clear. I am confident that I have done nothing illegal and I know that this matter will be cleared up," he said on a call with journalists and analysts from London, where he lives.
Asked if he regretted how things had turned out, he said: "Of course I do. It's not fun to be held captive for 10 days, and of course I regret this."
"Whilst I am of the firm opinion that there are no grounds for the current allegations against me, I do understand why the Norwegian Economic Crime Authority reacted to the transactions and hence the need to investigate," he said.
He had thought it was a joke when he was initially arrested in Sweden, he added.
Hexagon shares rose 1.6 percent on Monday as Rollen returned to work. It has emerged that he was under arrest when he presented Hexagon's third-quarter results in a conference call with analysts on Oct. 28.
Rollen said the briefing went ahead as planned because there was too little information about the Norwegian arrest warrant.
Rollen also fielded questions over his commitment to Hexagon in light of his activities with Greenbridge Partners, an investment firm founded with Hexagon chairman Melker Schorling.
"Greenbridge for me is an investment, it is not a job," he said. "But I do have the final say in certain investments, so I would regard it as a board assigment. And I have no other assignments but Greenbridge."
Hexagon shares have fallen 10 percent since last Monday when the firm announced that he had been detained by authorities, forcing investors to factor in a possible future without Rollen at the helm.
Asked how long he planned to stay on as CEO, Rollen told Reuters: "Hexagon, as I have said, is not at all as dependent on me today as 5 to 10 years ago. We have succession plans, just as any serious company," he said.
Norway's public prosecutor has said the investigation will continue.
The allegations concern an investment made in Next Biometrics in October last year by Iskossala Ltd, which bought shares on behalf of Greenbridge Partners Ltd.
A first purchase of 284,341 shares was made on Oct. 6 and 7, 2015. A couple of days later, on Oct. 8, Iskossala, the Rollen family's private investment firm, bought another 333,333 shares and also subscribed to a rights issue for 2,000,000 more shares, according to Hexagon.
Shares in fingerprint sensor maker Next Biometrics surged about 85 percent the day the Oct. 8 investment was announced.
All of the shares were transferred from Iskossala to Greenbridge in January this year when the latter became fully operational.
Rollen's lawyer said on the call that Norway's case lacked merit and that Rollen did not have insider information when the investment in Next Biometrics was made.
Reporting by Johannes Hellstrom and Mia Shanley; Editing by Adrian Croft/Keith Weir