Free agent Defensive end Mario Williams has signed a six-year deal with the Buffalo Bills, according to ESPN's Adam Schefter. ESPN's Chris Mortensen that said the Bills will hold a 1:30 press conference to announce the signing.

Both the Bills and Williams have engaged in heavy talks for the past three days since the start of free agency on Tuesday. The Bills announced on their website early Thursday that the star pass-rusher was at the team's headquarters.

ESPN reported that the Bills flew Williams into town via private jet from his home in North Carolina shortly after the free-agency period opened at 4 p.m. ET on Tuesday. Sports Illustrated reported that Williams spent then spent Tuesday night dining with team management and coaches at a downtown Buffalo restaurant. On Wednesday morning, Williams was joined by his fiancée, who traveled to Buffalo, and was provided a tour of the region after he took a physical and toured the Bills facility.

Williams could greatly improve the Bills' pass rush after it just managed just 29 sacks last season if he remains healthy. He was limited to just five games last season as a result of a torn chest muscle. Williams also missed three games in 2010 after having surgery to repair a sports hernia.

Williams, selected first overall in the 2006 draft by Houston, is a two-time Pro Bowler. He had a franchise-best 53 sacks in six seasons with the Texans, setting a single-season team record with 14 sacks in 2007.

Many argue that after quarterback Peyton Manning, Williams has been regarded as one of the top free agents available so far.