In early September, XPO Logistics agreed to pay $3 billion for Con-way, the less-than-truckload carrier.

Wall Street didn’t like the deal. Shares for the NYSE-traded XPO, a transportation and logistics company that provides truckload, air, and water transportation services, tumbled by nearly a third in September.

That was the case even though, according to XPO’s press release, the Con-way deal will double XPO’s annual earnings and add $15 billion in yearly revenues to the company. XPO’s announcement said it could improve Con-way’s operations and increase its operating profit by as much as $210 million in the next two years.

Why was Wall Street skeptical of XPO’s aggressive acquisition?

For one thing, XPO completed a deal earlier this year for Groupe Norbert Dentressangle, a French trucking firm. These deals mean that XPO is accumulating debt, which the company reported at $3.8 billion for the most recent quarter. Even though XPO’s acquisition strategy increases its revenues, which are expected to increase by over 750 percent by 2018 from $2.4 billion in 2014, not including the Con-way deal, investors are concerned that if XPO intends to grow through acquisitions, its debt levels could become unmanageable.

They are also concerned about whether XPO is departing from its historical business focus. XPO has always been an asset-light supply-chain management company rather than an operator of logistics assets. But XPO’s recent deals have the company buying transportation assets.

Will XPO be able to successfully integrate these new businesses? That’s another thing making investors nervous.

Peter Buxbaum is web editor of Global Trade.