FRANKFURT, June 23 (Reuters) - Trans-o-Flex is preparing to list on the Frankfurt stock exchange as early as September in a deal that could value the German logistics firm at roughly 1 billion euros ($1.2 billion), people close to the matter said.

The company is working with JPMorgan on the initial public offering that could see stock worth 300 million euros sold, three sources said.

"In order to finance our further growth, we are continuously evaluating possible financing options, including an IPO," a company spokesperson said.

JPMorgan declined to comment.

Benefiting from a general online shopping trend in the COVID-19 pandemic that boosted the business of most logistics firms, Trans-o-Flex last year saw sales increase by 4% to 515 million euros.

Trans-o-Flex - shorthand for Transportorganisation von besonderer Flexibilität or transport group with special flexibility - was founded in 1971 by five logistics entrepreneurs.

The Weinheim, Germany-based company specialises in transport services for the pharmaceutical, cosmetics and consumer electronic industries.

After being bought by conglomerate Haniel in 1985 and then by investors Schoeller and Amberger in 1995, Deutsche Post attempted a takeover, which was blocked by antitrust authorities in 1999.

Following years of ownership by private equity firm Odewald and then Oesterreichische Post, Schoeller and Amberger bought it back in 2016.

After a restructuring, Trans-o-Flex announced in 2019 that it had turned its first profit in 10 years. It later said that it has been profitable since. ($1 = 0.8373 euros) (Reporting by Arno Schuetze; Editing by Lisa Shumaker)