Shares of Garmin ( GRMN) slipped below $100 for the first time in nearly a month as investors continued to fear a bidding war caused by its attempt to buy Dutch mapmaker Tele Atlas.

Garmin was recently off $9.38, or 8.7%, to $98.02.

Earlier Thursday, Merrill Lynch downgraded the stock to sell on concerns that Garmin could ultimately have to raise its offer for Tele Atlas as it battles rival TomTom for control of the company.

Merrill's action offset a move Thursday by JMP Securities, which raised its price target on Garmin to $140 from $100, citing the underpenetrated personal navigation device market.

Garmin announced Wednesday that it planned to offer $3.3 billion for Tele Atlas, 15% higher than TomTom's July offer and a 48% premium to Tele Atlas' share price before TomTom's bid.