An “unsolicited” offer has been made for electronic clinical trials services provider etrials Worldwide, and Bio-Imaging has responded by upping its bid for the Morrisville-based firm by some $5 million.

The news sent etrials shares up more than 46 percent, or 37 cents, to $1.18 in late-morning trading.

On May 6, Bio-Imaging (Nasdaq: BITI), which is based in Newtown, Pa., and etrials (Nasdaq: ETWC) announced a $10 million buyout of etrials.

The latest move came “in response to an unsolicited offer received by etrials from an unrelated third party,” etrials and Bio-Imaging said.

Due to the outside bid, Bio-Imaging and etrials said Wednesday that they had rewritten their merger agreement. A package of shares and 62 cents in cash resulted in a new $1.35 per share offer for etrials.

The original offer was for 91 cents in cash (15 cents per share) and stock.

A third of etrials shareholders have already approved a merger, the companies said in a statement.

“I’m pleased that we are continuing to move forward with this acquisition given its strategic fit and benefit to our shareholders, customers and employees,” etrials Chief Executive Officer M. Denis Connaghan said.

etrials has suffered through a recent series of management changes and struggled to grow its business of providing software and related services to pharmaceutical and life science firms that are conducting clinical trials.

etrials has some 100 employees.