According to this news article a study by the National Cancer Institute of Italy, for one.

The coronavirus was circulating in Italy since September 2019, a study by the National Cancer Institute, INT, of the Italian city of Milan shows.

The World Health Organization has said COVID-19, the respiratory disease it causes, were unknown before the outbreak was first reported in Wuhan, in central China, in December.

Italy’s first COVID-19 patient was detected on 21 February in a little town near Milan, in the northern region of Lombardy.

But the Italian researchers’ findings, published by the INT’s scientific magazine Tumori Journal, show that 11.6 per cent of 959 healthy volunteers enrolled in a lung cancer screening trial between September 2019 and March 2020, had developed coronavirus antibodies well before February.

Edit: here's the Journal article they published

Abstract

There are no robust data on the real onset of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and spread in the prepandemic period worldwide. We investigated the presence of SARS-CoV-2 receptor-binding domain (RBD)–specific antibodies in blood samples of 959 asymptomatic individuals enrolled in a prospective lung cancer screening trial between September 2019 and March 2020 to track the date of onset, frequency, and temporal and geographic variations across the Italian regions. SARS-CoV-2 RBD-specific antibodies were detected in 111 of 959 (11.6%) individuals, starting from September 2019 (14%), with a cluster of positive cases (>30%) in the second week of February 2020 and the highest number (53.2%) in Lombardy. This study shows an unexpected very early circulation of SARS-CoV-2 among asymptomatic individuals in Italy several months before the first patient was identified, and clarifies the onset and spread of the coronavirus disease 2019 (COVID-19) pandemic. Finding SARS-CoV-2 antibodies in asymptomatic people before the COVID-19 outbreak in Italy may reshape the history of pandemic.